Zhang Guanghua, Gu Zonglin, Zhao Qiannan, Ren Jingqiu, Lu Weidang
School of Electrical Engineering and Information, Northeast Petroleum University, Daqing 163318, China.
College of Information Engineering, Zhejiang University of Technology, Hangzhou 310014, China.
Sensors (Basel). 2020 Feb 13;20(4):1016. doi: 10.3390/s20041016.
Sparse Code Multiple Access (SCMA) technology is a new multiple access scheme based on non-orthogonal spread spectrum technology, which was proposed by Huawei in 2014. In the algorithm application of this technology, the original Message Passing Algorithm (MPA) has slow convergence speed and high algorithm complexity. The threshold-based MPA has a high Bit Error Ratio (BER) when the threshold is low. In the Maximum logarithm Message Passing Algorithm (Max-log-MPA), the approximation method is used, which will cause some messages to be lost and the detection performance to be poor. Therefore, in order to solve the above problems, a Threshold-Based Max-log-MPA (T-Max-log-MPA) low complexity multiuser detection algorithm is proposed in this paper. The Maximum logarithm (Max-log) algorithm is combined with threshold setting, and the stability of user nodes is considered as a necessary condition for decision in the algorithm. Before message updating, the user information nodes are judged whether the necessary conditions for the stability of the user node have been met, and then the threshold is determined. Only users who meet the threshold condition and pass the necessary condition of user node stability can be decoded in advance. In the whole process, the logarithm domain MPA algorithm is used to convert an exp operation and a multiplication operation into a maximum value and addition operation. The simulation results show that the proposed algorithm can effectively reduce the computational complexity while ensuring the BER, and with the increase of signal-to-noise ratio, the effect of the Computational Complexity Reduction Ratio (CCRR) is more obvious.
稀疏码多址接入（SCMA）技术是一种基于非正交扩频技术的新型多址接入方案，由华为于2014年提出。在该技术的算法应用中，原始的消息传递算法（MPA）收敛速度慢且算法复杂度高。基于阈值的MPA在阈值较低时误码率较高。在最大对数消息传递算法（Max-log-MPA）中，使用了近似方法，这会导致一些消息丢失且检测性能较差。因此，为了解决上述问题，本文提出了一种基于阈值的Max-log-MPA（T-Max-log-MPA）低复杂度多用户检测算法。将最大对数（Max-log）算法与阈值设置相结合，并将用户节点的稳定性作为算法决策的必要条件。在消息更新之前，判断用户信息节点是否满足用户节点稳定性的必要条件，然后确定阈值。只有满足阈值条件且通过用户节点稳定性必要条件的用户才能提前解码。在整个过程中，采用对数域MPA算法将指数运算和乘法运算转换为最大值和加法运算。仿真结果表明，所提算法在保证误码率的同时能有效降低计算复杂度，并且随着信噪比的增加，计算复杂度降低率（CCRR）的效果更明显。
